This is a 5-year trial to test whether improvements in whole body insulin sensitivity can prevent or delay the development of non-insulin-dependent diabetes mellitus to Hispanic women identified to be at high risk for diabetes by history of gestational diabetes and by their oral glucose tolerance test profile when not pregnant. This investigator-initiated project is a direct result of information obtained on the prediction and mechanisms of NIDDM in women with GDM from a current NIH-funded cohort study (GCRC Protocol #626).